I find I like to use the same pick for everything, so I go with a happy medium, yellow Tortex Dunlop .73, on both guitar and mandolin. I also pick guitar tunes and try to be loud enough, and I don't find a thicker pick than that to be louder. Picks with no flex have a tendency to dig into the strings and get stuck there.
For strings I have just put Elixirs on both my cheap mandolin and my inexpensive but well-made mandola. In both cases they make the instrument sound twice as valuable.
Besides, I just started in a one-year college program and I figured I'd put one-year strings on everything I own while I still have bucks! (Quit my job yesterday!)